Method and apparatus for heat treating sheet metal



P. A. MEEHAN Dec. 6, 1932.

METHOD AND APPARATUS FOR HEAT TREATI'NG SHEET METAL Filed June 28 Patented Dec. 6, 1932 i nutren srares fraai?k Fries PAUL A.. lEEAN, F CLEVELAND, OER), ASSIGNOR, BY MESNE ASSIGNIFENT TU SWINDE'L'L-DR'ESSLER CRPORATION, 0F '.EITTSB'URGH,PENNSYLVANIA, A. CORPQRA.

METHOD .drm APPARATUS FOR HEAT TEEATNG @MET METAL rlhe present invention relates to .furnaces wherein a strip or metal in the form of wire strands or an elongated web of sheet metal is subjected to a continuous heattreating process. rThe object or" my invention is to provide an improved method oit and apparatus for continuously heat treating metai inv such a form. The apparatus of my invention is especially adapted for operation as a wire or sheet metal annealing furnace and is characterized by the construction or the furnace in such a manner as to permit a vertical passage therethrough of the material to he heat treated.

The various features oi novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part oie this specification. For a better understanding orn the invention., however, and the advantages possessed by it reference should be had to the accompanying drawing and descriptive matter in which l have illustrated and described preferred embodiments of the invention.

@i the drawing:

llig. l is an elevation in section of apreerred form oi my invention;

hier. 2 is an enlarged side view of a portion apparatus shown in Fig. 1;

3 is a section on the line 3-3 of Fig. 2; el is a sectional elevation of a portion .iodiedorm of my invention;

` ig. 5 is a section through the heating zone illustrating a modiied form of heating wneans; and

Fig. 6 is a section through the heating zone illustrating another form and arrangement of heating elements.

ln the drawing l have illustrated a furnace structure A wherein a continuous weber strip or sheet metal B is subjected to annealing treatments and which may be regarded as comprising a vertical series of treatment zones including a low temperature or preliminary heatingn zone a, a high temperature or soaking zone and a cooling zone c. ln the construction shown, the furnace A is substantially rectangular in cross section and arranged to permit the free passage of the strip of sheet metal B from the top to the bottom of the furnace. .dt the top of the urnace is a platform C on which is mounted for rotation a large size drum, roll or pulley C on the periphery oi which the strip B ci sheet metal is supported and passed tothe furnace preheating zone a. At the top ci the preheating .zone is arranged a chamber D, the opposite sides of which are arranged with outlets D to a stack D2 provided with a draft regulating valve DE. At the top of the cham ber D are arran ed a pair oi centering rollers D4 between which the strip ot metal to be heat treated is passed downward and which prevent the heating gases from escaping through the top of the passage. A. vertical rectangularly saped passage DE extends from the bottom or the chamber D to the top of the high temperature heating chamber E of the heating zone The heating zone t comprises the vertical heating chamber l wherein two series F', F2 or vertically spaced burners F are located in burner openings in opposite sides or the heating chamber. The burner openings for each set oit burners are spaced horizontally from the openings of the adjoining series so that the burning mixture from each burner is discharged between the side wall and the descending strip or sheet metal. Each burner lF comprises a cylindrical pipe element having a tapered nozzle haat the inner end thereoi1 and connected at its outer end through a valve F7 to a group main F4 into which the burners in that section of the heating chamber are connected. fis shown in Fig. 2 each group main Ft has four burner elements of each series on one side ot the heating chamber connected thereto and is in turn connected to a gas main F5 by a valved connection F". At vertically spaced points in the furnace side walls are openings G opening to the interior of the 'furnace at various sides thereof and to which access is had by platforms C secured to the furnace wall and connected to an elevator shaft G2. These openings Gr may be used for inspection or cleaning operation and are especially useful for the insertion of suitable tools by which the material to be treated may be initially threaded through the guide rolls. The

openings are closed at their outer ends by closure devices G. The bottom of the heat- 'ing chamber is formed by an inverted V- shaped wall portion E having a vertical rectangular shaped passage E2 through the apex thereof. At the upper endl of thepassage is mounted a pair of adjustable guide rollers Es formed of heat resistant material for the strip of sheet metal B.

The wall portion E forms theY top of a vertical cooling chamber H in the cooling zone c. The cooling chamber comprises two lhorizontally spaced series; of cooling elements H and H2, each series comprising vertically spaced horizontal elements each of which is connected at its opposite ends to the adjacent upper and lower cooling elements, respectively. A cooling medium, such as water, is introduced into each series of elements through an inlet pipe Ha at the bottom of each series and passes out at the topV of the series through outlet pipe H4.

At the bottom of the cooling chamber H is arranged an inclined bottom wall Hls similar in construction to the wall E' and provided with a restricted passage Hs through the central portionthereof. At the upper end of the restricted passage is arranged a pair of adjustable rollers H10 between which the strip or web of sheet metal is guided. Each rollerl of the guide roller pairs EB and H10 is rotatable on a shaft A2, which extends parallel to the strip B and with each end projecting through a horizontal slot A3 formed in the adjacent side wall of the furnace A. Each shaft is normally fixed in a predetermined position in the corresponding slots by any suitable holding means A4. Each l'pair of rollers can be moved towards or away from each other by loosening the holdin means, varying the position of the shaft en in the corresponding slots, and again tightening theholding means. The cooling chamber is also provided at vertically spacedpoints in the side walls thereof with inlet pipes H7 through which reducing gases are introduced into the cooling chamber. The lower portion of the furnace below the bottom wall of the cooling chamber is provided with a pair of outletv pipes H8 in opposite side walls of the furnace and connected at their outer lends to a fan H", so that any gases formed in the sec-` ber. Mounted in the tank lare a pair of rotatable drums or pulleys J and J 2, the drum J being located 'with one part of its peripheral portion in line with the opposite portion of the periphery of the drum C at the top of the furnace so that the strip of sheet metal will pass downward through the fur nace without contacting with any of the parts thereof except the ide rolls D, E2 and H1 and around the rum J to the drum J2 from which it passes to the pickling baths (not shown). -Y

In the operation of the furnace described, a continuous strip of sheet metal B, which may be formed by spot welding strips rolled from billets, is passed downward through the preheating zone a where it is heated by the gases arising from the high temperature heating zone b. The heat transference in this section is ve the gases 1n the restricted passage D*s with the descending sheet metal. The strip then passes through the heating zone b wherein it is heated to the desired temperature. Bv

high dueto the close contact of :3:

controlling the burner valves, the nal teniperature to which thestrip isheated may be closely regulated. The burner provisions are of the premixing type, wherein the air and gas are already mixed before issuin from the burner nozzles. It is desirable t at the burners be so regulated that a reducing atmosphere be maintained within the heating chamber E, since in annealing operations the metal sheets or strands of wire being heat treated should not be exposed to oxidizin conditions when the metal is at the hig tem eratures to which it is ordinarily heated.

A sight pressure is maintained within the heating chamber E to prevent any -upw'ard movement of the atmosphere in the `cooling chamber H into the heating chamber.

The strip `of sheet metal then passes downward between the guide rolls Es throu h the vertical passages into the cooling cham er H, where due to the direction of flow of the cooling medium through the pipe elements H and H2 being opposite to the direction of travel of the strip of metal, the metal is slowly cooled inits downward passage and passes through the passage HB into the tank J. The restricted passage E2 at the upper end of the cooling chamber tends to further preventV any upward movement of the cooling atmosphere. The introduction of reducing gases through the inlet pipes H1 tends to build up a small 7-1 pressure in the cooling chamber which would eep the metal' from being oxidized during its passage through the cooling chamber.

Any leakage of the cooling chamber atmosphere downward through the passage` Ha would be drawn off by the fan H9 and any leakage up through thepassage- E2 would pass off with the combustion gases.

The strip of metal passing throughv the tank J is stillat a temperature suiicient to' generate a quantity ofsteam which collects in the portion of the furnace below the wall i l H*s and which-is prevented from passing upwardly through the restricted passage H by the action of the fan H. The final stage of y metal, a disadvantage occurring in horizontal annealing furnaces, and is further characterized bythe gravity circulation of the gases in the heating and cooling zones as the hot gases in the heating chamber naturally tend to rise and ilow upward through the preheating` zone to the` stack while the colder gases in the cooling chamber tend to remain in that position. The combustion conditions in the heating; zone may be so regulated that a slight pressure in that zone will he sudicient to prevent any movement ot the gases into or from t`ie heating' chamber to the cooling chamher. 'further advantage ot my invention is that less ground space is occupied hy a vertical 'furnace than hy existing types of: horizontal annealing' furnaces. The furnace illustrated is capable of handlingstrips ot sheet metal up to a maximum width ot 24" and is especially adapted "for the annealing of automohile tender stock, which is approximately l in width.

Various modilications oii the type-ot tur` nace construction shown in Figs. l-3 may he made, one of which is illustrated in Fig'. ll, l

wherein parallel webs or strips of sheet metal E and B2 are passed downward simultaneously over corresponding drums C1". ln this modiiied construction the heating chamber is provided with three vertical series of hurner elements F10, F20, F in openings in opposite sides o't the heating' chamber, the hurner series being horizontally spaced so that each strip ot metal will he evenly heated on all sides. ils shown the turnace is constructed with a duplicate set ot restricted passages D50 similar to the passage D5 shown in 2, through which the strips are separately passed.

@ther means may he provided tor heating' the strip Iin the preheating zone a and heating' zone such as electrical resistors on either side of the sheet metal or, as shown in section in Fig. 5, vertical combustion chamhers F40 and F50 through which the heating gases pass and which extend through the heating and prehcating zones. rlhe combustion chambers are arranged with their adia cent sidesspaced apart to provide a narrow passage B10, like the passage D5, -through which the metal strip B may he passed. ln such constructions, the proper 'furnace atmosphere may he introduced into the bottom ot' the passage to provide reducing conditions therein so that there will loe no oxidation ot the sheet metal during the annealing operations. v

A further modied form of heating means is illustrated in Fig. 6 wherein the burner nozzles F5 are so arranged that the ignited mixtures are discharged against thev side walls of the heating chamber which are parallel with the material being heated. ln this construction the material is mainly heated by radiation from the side walls of the heating chamber.

While in accordance with theprovisions ot the statutes, l have illustrated and descriloed the loest orm of embodiment ol my invention now hnown to Ine, it will he apparent to those skilled in the art that changes may he made in the form et the apparatus disclosed without departing troni the spirit oi my invention as set 'forth in the appended claims and that in some cases certain 'features of my invention may he use'y to advantafe without a corresponding use or other features. Having now descrihed my invention, what l claim as new and desire to secure hy Letters Patent, iszl. rEhe method of annealing sheet metal of a substantial width which comprises passing' a continuous strip of the metal downwardly throurh a series ot heating chambers out of contact the apparatus therein and in which the metallic strip is progressively heated to a high temperature hy radiation and convection, slowly cooling` said strip during its passage through a cooling chamber, maintaining: said strip in a reducing' atmosphere while in said heating and cooling chambers., and subjecting the strip while in an unoXidized condition to a final cooling' action hv passingP it through a hath ot cooling liquid.

2. The method of' annealing sheet metal ot a suhstantial width which comprises passino; a continuous strip o the metal vertically downward through a low temperature preheating zone in which heat is transferred to the metal hy convection, a hia'h temperature heating zone in 1which heat is transferred to the metal partly hy convection and partly hv radiation and wherein a reducing atmosphere is maintained. and a cooling zone. throng-h which a cooling Jduid is passed in a direction opposite to the travel of the metal strip, and regulating the combustion condil tions in said heating zone to prevent the circulation ot gases hetween said heating and cooling zones.

'3. A vertical 'furnace tor subjecting a continuous strip ot sheet metal to heat treatment comprising a vertically elongated heating' chamber, heat-ing means arranged in said chamber at opposite sides of said strip. means tor moving said strip downwardly through said chamber, and guiding; means at one level in said chamber at opposite sides of said strip maintaining said strip out of Contact with said heating means While passing through Said chamber.

4. A furnace for subjecting a continuous Y strip of sheet metal to heat treatment comprising a vertically elongated heating chamber, guiding means for causing the strip of sheet metal to move vertically through said chamber and means for causing heating gases to move through said chamber in a direction opposite to the movementof said metal strip.

y 5.' A furnace adapted for heat treating a continuous strip of sheet metal of a substantial width and comprising a vertically elongated preheating chamber, a vertically elongated heating chamber in vertical alignment with said preheatingchamber and connected thereto, a vertically elongated cooling chamber in vertical alignment with said heating chamber, and means for passing a continuous trip of metal vertically through said cham- 6. A vertical annealing furnace comprising a preheating chamber, means connected to the temperature zone into intimate contact with said strip while passing through said preheating zone and supplying heat to said strip while passing through said high temperature zone by radiation and convection, slowly cool- June, A. D. 1927.'

PAUL A. MEEHAN.

upper end thereof for effecting an upward heating gas ow therethrough, a vertically elongated heating chamber having its upper end connected to said preheatingv chamber, 4means for passing a continuous strip of metal vertically downward through said chambers, heating means in said heating chamber at opposite sides of said strip of metal, and means preventing contact between said strip and heating means.

7 An annealing furnace comprising a preheating chamber, a heating chamber, said preheating chamber being connected to said heating chamber andarranged to receive heating gases therefrom, means for passing a strip of 40 metal vertically through said chambers' and from the top of said preheating chamber.

8. An annealing furnace comprising a preheating chamber, a heating chamber and a cooling chamber, means lfor passing a continuous strip of sheet metal through said chambers, means for withdrawing heating gases from said heating chamber through said preheating chamber, means in said heating chamber for simultaneously heating both sides of said metal strip, means for maintaining a. re-

. ducing atmosphere in said heating chamber,

, means in said cooling chamber for simultaneously cooling both sides of said metalstrip,

5 and heat resistant guide means at vertically metal strip is prevented from the walls ofsaid chambers.

9. The method of annealing a continuous strip of metal which comprises passing the strip vertically downward successively through a preheatin zone, a high temperature heating zone an a cooling zone, progressively heating said strip while passing throu h the preheating and hightemperature zones contacting with c spaced points in said furnace by which said means for withdrawing the heating gases temperature and preheating y passing heatinggases from said high i 

